The present invention relates to a device for reading information carried on a data bus, and more particularly a device without a wired connection to the network. The invention is intended more particularly for the field of the onboard networks (automobile, transport, automation, aircraft . . . ). The invention can also be applied to other fields like data processing. The reading device of the invention permits recovery of the data of the network while preserving the integrity of wiring.
The object of the invention includes recovering the data exchanged on a digital communication bus. A communication bus is made of one or a plurality lines, each line can be configured as a metal conductor and its insulator.
The reading device, disposed on one or more of the lines, is free from a physical contact with the conducting part of the line. The invention is related more particularly to the multiplexed networks on paired wires of the copper type which equip all the new vehicles today, and in particular the network known by the name “CAN” (Controller Area Network) bus. The CAN, defined in various standards (ISO 11898-2, ISO11898-3, SAE J2411) according to the speed or the number of communication lines used, is the communications protocol by far more used today in the world manufacturers. But the invention could be generalized to other onboard networks (VAN, LIN, Flexray, AFDX . . . ), and with all the communication systems for digital network with physical support conductors permitting a coupling of the capacitive type.
The invention proposes a means of recovering the data circulating on a digital data bus (in fact the network CAN) of a vehicle without touching the physical integrity of the network.
Today, on the majority of the vehicles equipped with a CAN network, the manufacturers decline any responsibility if equipment of a “2nd party” including an intimate connection to their CAN bus is assembled on the vehicle. It is thus strongly advised making splices on the wiring harness of the vehicle.
Some connectable equipment for diagnostics is possibly tolerated by certain manufacturers. But this type of connection does not solve all of the problems. Certain CAN networks are not accessible for this capture and the obstruction of such a connection is not desirable in certain vehicles. The manufacturers refuse that other equipment is connected on their CAN bus, if they modify the topology and the electric characteristics of the network (problem of waking or nonwaking of the electronic assembly or parts of the of the modified vehicle for example).
Today, it there not of powerful solution making it possible to recover the CAN data on the vehicle without touching with the integrity of the network while guaranteeing a connection simple to carry out and stable in the time and with a correct cover rate (a number of messages received through device/a number of messages exchanged on the medium).
A solution exists today in Germany, to connect itself on the vehicle by preserving the integrity of the network. It uses the principle of the inductive coupling but present of this fact certain problems:                Obstruction of the clip which is a reel being able to be bulky for this type of applications        the current version of the grip poses problems in time because it is not sufficiently fixed at the cable.        the principle of the inductive coupling is depend on the current fluctuations on the espionnée line. So that, according to the position of the grip on the network, a certain number of information can be mal-interprêtées        the current version of the grip is not compatible with the whole speeds and technologies CAN now available. To cover the range of the configurations, one needs several of the same clips principle but for the different adjustments.        weak or poor Cover (a number of messages received through device/a number of messages exchanged on the medium).        